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A discovery in Antarctica has offered fresh insights into the ancient formation of New Zealand's Southern Alps.

A study led by French and Israeli scientists revealed how two tectonic plates fused to form a single Antarctic Plate 15 million years later than originally predicted.

Their findings, just published in the scientific journal Nature Communications, hold major implications for understanding of the tectono-volcanic activity surrounding the Pacific Ocean, from the rise of the South Island's mountainous spine to California's geology.

The motion between East Antarctic and West Antarctic Plates accommodated along the length of this rift created one of the longest mountain ranges in the world - the Transantarctic Mountains.

It also caused the eruption of hundreds of volcanoes, mostly under the ice sheets, and shaped the sub-ice topography.

These motions dictated, and still dictate, the heat flow rate that the crust releases under the ice and was one of the factors controlling the rate by which the glaciers were advancing toward the surrounding southern ocean.

GPS data and a lack of seismic activity suggest that the rift in Antarctica was no longer tectonically active.

But there had been other unanswered questions - namely, how did the plates drift relative to each other over the last 26 million years, and when did the rift stop being active?

Marine magnetic data collected near the northern edge of the West Antarctic rift system showed that motion which was assumed to have ended abruptly 26 million years ago, actually continued for another 15 million years.

A rift between East Antarctic and West Antarctic Plates created one of the longest mountain ranges in the world - the Transantarctic Mountains. Photo / File

"Since Antarctica tectonically connects the Pacific Plate to the rest of the world, these results have important ramifications for understanding the tectonic evolution around the Pacific Ocean - the rise of New Zealand's Alpine Mountains, motions along the San Andreas Fault in California, and more," said Dr Roi Granot, of Israel's Ben-Gurion University of the Negev.

"Antarctica forms an important link in the global plate tectonic circuits which enable to calculate the motion along different plate boundaries.

"Understanding past plate motions between East and West Antarctica therefore affects our ability to accurately predict the kinematic evolutions of other plate boundaries."

Professor Rupert Sutherland, of Victoria University's School of Geography, Environment and Earth Sciences, said the new findings wouldn't change our understanding of today's level of motion along the Australian and Pacific plate boundary which New Zealand straddled.

"But it would change things for the period between 10 and 25 million years ago, in the early part of the Neogene, when the Alpine Fault was forming," Sutherland said.

"While the difference would still be quite incremental, the actual business of trying to accurately work out the history of global plate motions is an essential piece of the puzzle in understanding plate tectonics."

Sutherland expected there were still significant riddles to be solved - particularly, precisely how the furious Pacific Ring of Fire was born.